A wiring substrate adapted for a large electric current, such as a control substrate for a high-output motor mounted in an electric or hybrid vehicle, is used in combination with a bus bar to allow a large electric current to flow, as disclosed in Patent Document 1. Also, Patent Document 2 discloses a method for manufacturing a circuit substrate by arranging a conductor plate, in which a large electric current is to flow, between molding dies and then supplying resin into the dies.